Strata 3D CX 7 has Normal mapping, which is a very welcome addition, but… what are normal maps, and what is their difference with bump maps?
Both bump maps and normal maps simulate a relief that is not there by “tricking” the rendering engine to use different normals than the real surface normals. What is a normal, then?
A normal is a vector perpendicular to a surface. When using bump mapping, the (grayscale) pixel luminosity information would represent a higher or a lower surface, but always in the same direction of the geometry normal. Bump maps are sometimes called “1D bump maps”
When using normal mapping, the vector can point in any direction from the surface, with the x,y, and z axis information for the normal vector encoded into a RGB image. That’s why bump maps are grayscale and Normal maps are in color. Normal maps are sometimes called “3D bump maps”
Normals in Bump maps, all pointing in one dimension. The “height” of the surface is calculated from the grayscale values of each pixel. White is raised, black is recessed, 50% gray is level with the surface.
Normals in Normal maps, pointing in different directions in 3D space. The values are taken from the RGB values for each pixel.
The difference between Bump and Normal mapping is remarkable.
Bump-mapped tiles
Same tiles, normal mapped
How do we create normal maps?
A good question is how do we create normal maps.
The simplest answer, and the one I use, is creating a bump map in Photoshop like we are used to, and then convert it into a normal map using a Photoshop script named nDo, which we can download for free from this link.
This script allows us to convert grayscale bump maps into normal maps with good results.
A bump map
Bump map converted into Normal map with nDo
The easiest way to run the script is to remember where you unzipped it and then execute it using File>Scripts>Browse… and navigating to where you have the nDo.jsx file.
You can find more about nDo here.
There we have a better way of representing relief that is not there in our scenes.
